rs53576 is a silent G to A change in the oxytocin receptor (OXTR) gene. Studies have demonstrated that individuals with the G allele are more empathetic, feel less lonely, employ more sensitive parenting techniques, and have lower rates of autism (discussed in [PMID 20724662])

The blog Not Exactly Rocket Science discusses that Americans with (G;G) tend to be more sensitive parents, more empathetic and less lonely than those with an ‘A’. In a Korean population people with (G;G) were less likely to seek support from their peers.

[PMID 19934046] Oxytocin receptor genetic variation relates to empathy and stress reactivity in humans. In brief, people with the G;G genotype were better able to discern the emotional state of others than those who carried the A-allele (blog summary found here). The study encompassed 192 participants of both sexes and mixed ethnicities. The study subjects underwent a number of tests to determine their level of empathy and stress reactivity. They found that G;G individuals performed significantly better on the behavioral measure of empathy and were 22.7% less likely to make a mistake on the "Reading the Mind in the Eyes Test" (RMET) (a behavioural measure of empathic accuracy) than A;A/A;G individuals (P = 0.005). Similarly, G;G individuals reported higher levels of dispositional empathy than A;A/A;G individuals: mean (SE) = 3.69 (0.06) and 3.53 (0.04) for G;G and A;A/A;G, respectively (P = 0.025), and were less affected by stress (as measured by their heart rates): mean (SE) = 72.1 (0.54) and 78.4 (1.19) for G;G and A;A/A;G, respectively.

[PMID 19015103] This study examined the association between the OXTR gene and parenting. A total of 176 mothers of toddlers were included in the study. After controlling for marital discord, depression, and education status, rs53576 was found to significantly correlate with parenting, with the G;G genotype being associated with a significantly more sensitive parenting style than A;A or A;G genotypes. However, they concluded that the major factor influencing parenting was the maternal education level.

[PMID 22069391] Forty-five female subjects (17 twin pairs and 11 twins without their sibling) were genotyped and tested for their ability to hear and understand conversations in noisy environments. Participants with the G;G genotype reported less difficulty hearing and understanding (difficulty hearing total score [Mean (SD)], 9.2 (4.2)) than participants with A;A/A;G genotypes (13.9 (3.8); p < 0.001). Even after adjusting for age, the relationship between genotype and difficulty hearing scores was still significant (p = 0.003).

[PMID 22123970] Two hundred three healthy German male university students (mean age 23.2 y, SD 2.9 y) were subjected to a mock interview and their saliva cortisol levels were tested before and at a number of time points after the interview. Half of the participants were told to bring a female friend as social support, whereas the other half came alone to the interview. The authors found that subjects carrying the G allele (G;G or A;G genotypes) had significantly lower cortisol responses to stress when they had social support (P < 0.01). Conversely, there were no differences in cortisol levels in subjects with the A;A genotype receiving or not receiving social support (P = 0.46). Moreover, there was a trend (P = 0.08) for people with the A;A genotype to display higher levels of cortisol throughout the session than G carriers (no differences between the genotypes were observed at baseline).

[PMID 20647384] In this study, 345 healthy subjects were examined by multimodal neuroimaging techniques to identify structural and functional alterations in OXTR risk allele carriers and their link to temperament. The authors found that there was a significant association between the different rs53576 genotypes and grey matter volume in the hypothalamus, with the hypothalamus volume being significantly larger in G;G carriers than in A;A carriers (P = 0.012). Moreover, they investigated the relationship between rs53576 and reward dependence (RD) using the Tridimensional Personality Questionnaire, and found that the G;G, G;A, and A;A genotypes were associated with the highest, intermediate, and lowest RD values, respectively (G;G vs. A;A, p=0.02; A;G vs. A;A, p=0.07). Lastly, they also demonstrated that rs53576 is associated with amygdala activation, with the A;A genotype being associated with a significant reduction in activation compared to the G;G genotype (p=0.036); and with the functional relationship between the amygdala and the hypothalamus, with A;A carrier having a significantly increased functional correlation (p=0.036). The authors concluded that there is likely a neural mechanism linking both structural and neural signalling alterations in the oxytocinergic system to individual differences in emotional reactivity and prosocial temperament.

[PMID 17383819] Association of the oxytocin receptor gene (OXTR) in Caucasian children and adolescents with autism. This study found that there is no association between rs53576 variants and the risk of autism in Caucasian children and adolescents.

[PMID 22084107] Thin-slicing study of the oxytocin receptor (OXTR) gene and the evaluation and expression of the prosocial disposition

Followup:

[PMID 22499788] Misuse of hierarchical linear models overstates the significance of a reported association between OXTR and prosociality.